Snow bicycles are well known. U.S. Pat. No. 1,261,204 (Barton 1918) and U.S. Pat. No. 1,281,980 (Kostewich 1918) are early examples of snow bicycles. Some more recent examples include U.S. patents: U.S. Pat. No. 5,423,559 (Rhode 1995); U.S. Pat. No. 5,738,361 (Landucci 1998); U.S. Pat. No. 6,511,079 U.S. Pat. No. 6,626,258 (Forbes 2003); and U.S. Pat. No. 6,663,117 (Cheney et al 2003). A rear drive assembly for a snow bicycle which is believed to represent the closest known prior art is Canadian Patent Application 2,154,729.